The proposed research is designed to test the hypothesis that modulation of gonadotropin receptors, their intracellular messenger systems (e.g., adenylate cyclase) or the coupling of these membrane components is an important mechanism regulating the primate corpus luteum during the menstrual cycle and early pregnancy. Based on progress in this laboratory, the metabolism of arachidonic acid in the corpus luteum will be modified: (1) to identify products (e.g., prostaglandins) , which have local luteotropic or luteolytic actions during the menstrual cycle, and (2) to examine the effects of these paracrine factors on the gonadotropin receptor-adenylate cyclase system in luteal tissue. Studies are also planned in a novel model of early pregnancy: (3) to investigate the mechanisms resulting in homologous desensitization of adenylate cyclase in the primate corpus luteum during CG exposure, and (4) to define the relationship between changes in the gonadotropin receptor-adenylate cyclase system and the steroidogenic and peptidergic funtions of the corpus luteum. The adult, female rhesus monkey continues as the animal of choice for this project. Arachidonate metabolism will be modulated and monitored by drug infusions directly into the corpus luteum and blood collection from the utero-ovarian vein (and aorta), respectively. Levels of progesterone, LH and prostaglandins in the blood will be measured by radioimmunoassay. A regimen of human CG which invokes pregnancy-like patterns of circulating gonadotropin will be employed to simulate the rescue of the corpus luteum in early pregnancy. Adenylate cyclase activity will be assessed by the conversion of (alpha 32P)ATP to (32P) cyclic AMP. Available and occupied receptors will be characterized via specific 125I-hCG binding and radioimmunoassay of eluted CG, respectively. Crosslinked (125I)hCG-receptors will be solubilized and subjected to column chromatography and SDS-gel electrophoresis. Luteal cells from simulated early pregnancy will be incubated in vitro to discern their response to gonadotropins, prostaglandins and analogs of intracellular messengers (e.g., dibutryl cyclic AMP, a Ca+2 ionophore A23178 and oleoylacetylglycerol). These studies will (a) broaden our understanding of the gonadotropin receptor-second messenger systems in primate species, and (b) help elucidate the endocrine and paracrine processes regulating luteal function during the menstrual cycle and early pregnancy, with direct application to controlling fertility and infertility in women.